Leaching from Arsenic- Bearing Solid Residuals Landfill Conditions

Persistent Link:
http://hdl.handle.net/10150/195871
Title:
Leaching from Arsenic- Bearing Solid Residuals Landfill Conditions
Author:
Ghosh, Amlan
Issue Date:
2005
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The recent lowering of the arsenic MCL from 50 ppb to 10 ppb in 2006 will cause many utilities to implement new technologies for arsenic removal. Most of the affected utilities are expected to use adsorption onto solid sorbents for arsenic removal, especially in the arid Southwest, where conserving and re-using water is of utmost importance. This would cause the generation of more than 6 million pounds of arsenic residuals every year, which then would be disposed of in landfills. This thesis effort focuses on the testing of different aluminum and iron (hydr)-oxide based sorbents that are likely to be used for arsenic removal and assessing the behavior of these Arsenic Bearing Solid Residuals (ABSRs) under landfill conditions. It was demonstrated that the Toxicity Characteristic Leaching Procedure (TCLP) test underestimates the arsenic mobilization in landfills. Desorption of arsenic from ABSRs was quantified as a function of the range of pH and concentrations of competitive anions like phosphate, bicarbonate, sulfate and silicate and NOM found in landfills. The effect of pH is much more significant than the anions and NOM. Arsenic release due to competition of different anions is neither additive nor purely competitive. Landfill conditions were simulated inside long-term, continuous flow-through column reactors, and arsenic mobilization from sorbents was measured under those conditions. The results indicate that under reducing conditions, and in the presence of other competitive anions and high organics, microbes reduce arsenate to arsenite, which is a much more mobile species. Fe(III) is also reduced to Fe(II) under these conditions. Arsenic is transported in the particulate phase, associated with the iron, much more than in the dissolved phase. It was also observed that the sorbent itself might leach away at a faster rate than the arsenic sorbate causing a depletion of surface sites and a sudden spike in the release rate of arsenic, after a long residence time. Finally, investigation of different solid sorbents indicate, that the rate of leaching and the form of arsenic released varies widely and is independent of the respective adsorption capacities, even under similar leaching conditions.
Type:
text; Electronic Dissertation
Keywords:
arsenic; leaching; landfill conditions; solid sorbents
Degree Name:
PhD
Degree Level:
doctoral
Degree Program:
Environmental Engineering; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Ela, Wendell P
Committee Chair:
Ela, Wendell P

Full metadata record

DC FieldValue Language
dc.language.isoENen_US
dc.titleLeaching from Arsenic- Bearing Solid Residuals Landfill Conditionsen_US
dc.creatorGhosh, Amlanen_US
dc.contributor.authorGhosh, Amlanen_US
dc.date.issued2005en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe recent lowering of the arsenic MCL from 50 ppb to 10 ppb in 2006 will cause many utilities to implement new technologies for arsenic removal. Most of the affected utilities are expected to use adsorption onto solid sorbents for arsenic removal, especially in the arid Southwest, where conserving and re-using water is of utmost importance. This would cause the generation of more than 6 million pounds of arsenic residuals every year, which then would be disposed of in landfills. This thesis effort focuses on the testing of different aluminum and iron (hydr)-oxide based sorbents that are likely to be used for arsenic removal and assessing the behavior of these Arsenic Bearing Solid Residuals (ABSRs) under landfill conditions. It was demonstrated that the Toxicity Characteristic Leaching Procedure (TCLP) test underestimates the arsenic mobilization in landfills. Desorption of arsenic from ABSRs was quantified as a function of the range of pH and concentrations of competitive anions like phosphate, bicarbonate, sulfate and silicate and NOM found in landfills. The effect of pH is much more significant than the anions and NOM. Arsenic release due to competition of different anions is neither additive nor purely competitive. Landfill conditions were simulated inside long-term, continuous flow-through column reactors, and arsenic mobilization from sorbents was measured under those conditions. The results indicate that under reducing conditions, and in the presence of other competitive anions and high organics, microbes reduce arsenate to arsenite, which is a much more mobile species. Fe(III) is also reduced to Fe(II) under these conditions. Arsenic is transported in the particulate phase, associated with the iron, much more than in the dissolved phase. It was also observed that the sorbent itself might leach away at a faster rate than the arsenic sorbate causing a depletion of surface sites and a sudden spike in the release rate of arsenic, after a long residence time. Finally, investigation of different solid sorbents indicate, that the rate of leaching and the form of arsenic released varies widely and is independent of the respective adsorption capacities, even under similar leaching conditions.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectarsenicen_US
dc.subjectleachingen_US
dc.subjectlandfill conditionsen_US
dc.subjectsolid sorbentsen_US
thesis.degree.namePhDen_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineEnvironmental Engineeringen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorEla, Wendell Pen_US
dc.contributor.chairEla, Wendell Pen_US
dc.contributor.committeememberSaez, A. Eduardoen_US
dc.contributor.committeememberField, Jamesen_US
dc.identifier.proquest1227en_US
dc.identifier.oclc137354475en_US
All Items in UA Campus Repository are protected by copyright, with all rights reserved, unless otherwise indicated.